This invention relates to the use of aromatic hydrocarbon oils as total or partial replacements for the surfactants used in rigid and flexible polyurethane foams.
It is known in the manufacturer of solid polyurethane resins to extend the compositions with aromatic hydrocarbon oils. See U.S. Pat. No. 3,846,355 which discloses the use of paraffinic or olefinic hydrocarbon oils low in aromatic content, preferably high boiling petroleum fractions such as mineral oils, fuel oils, kerosenes, and conventional lubricating oils having a boiling point at atmospheric pressure of about 150.degree. C. (302.degree. F.), in amounts of at least 20 wt. % as extenders. It is also known in the manufacture of foamed flexible polyurethanes to use hydrocarbon oil extenders to plasticize and lower the end cost of a formulation (in amounts of 20% by weight or above). Coal tar products have also been used to replace part of the polyols used in the preparation of flexible polyurethanes.
It is known in the manufacturer of cellular polymeric materials such as polyurethane foams to use small quantities of various cell stabilizing additives in order to improve the foam's quality. The various foam stabilizers used have included polysiloxanes (see U.S. Pat. No. 2,901,445); trihalo alkyl silanes (U.S. Pat. No. 3,061,556); polydimethylsiloxane-polyoxy-alkylene copolymers (U.S. Pat. No. 4,031,044); copolymers consisting of polydimethylsiloxanes to which are attached various pendant groups (U.S. Pat. Nos. 2,901,445; 3,905,924; 3,839,384; 4,306,035; 3,884,847; 4,110,272; 4,067,828; 4,039,490); polysiloxanepolyoxyalkylene copolymers where the polyoxyalkylalkylene portions are end-capped (U.S. Pat. No. 4,478,957); polyether silicone copolymers with hydroxy terminated pendant groups (U.S. Pat. No. 4,769,174); a mixture of a high molecular weight silicone-oxyalkylene copolymer with a low molecular weight siloxane-oxyalkylene copolymer (U.S. Pat. No. 4,119,582); low viscosity alkoxy-modified siloxanes and low viscosity dimethylsilicone oils (U.S. Pat. No. 4,042,540); cyanosiloxanes (U.S. Pat. No. 3,905,924); aralkylsiloxanes (U.S. Pat. No. 3,839,384); siloxane-oxyalkylene copolymers and mixtures thereof with each other or with dimethylsilicone oils (see U.S. Pat. No. 3,741,917); high molecular weight silicate esters of polyether alcohols (U.S. Pat. No. 3,935,133); organosiloxane copolymers containing C.sub.5 -C.sub.20 alkyl groups (U.S. Pat. No. 4,299,923); low molecular weight C.sub.5 -C.sub.18 - alkoxysilicone compositions containing from 1 to 18 silicone atoms (U.S. Pat. No. 4,306,035); siloxane copolymer mixtures (U.S. Pat. No. 4,309,508); unsaturated polyoxyalkylene adduct/fumarate diester reaction products (U.S. Pat. No. 4,572,919); capped reaction products of an alkoxylated amine and a copolymerizable mixture of dialkyl maleate and N-vinyl-2-pyrrolidinone or N-vinyl caprolactam (U.S. Pat. No. 4,140,842); and polyoxyalkylene/unsaturated diester reaction products (U.S. Pat. No. 4,365,024).
Many of the the above stabilizers (often referred to as surfactants) are relatively expensive and can cause problems. For example, in the production of flexible polyurethane foams, the well-known polysiloxane-polyoxy-alkylene copolymers used as foam stabilizers cause the resulting foam to shrink to such an extent that it is difficult or impossible to obtain an open cell structure even by crushing the cell membranes. If no foam stabilizer is used, the foam becomes very coarse and the foam collapses. For example, the well-known silicone and siloxane surfactants, when used with tin catalysts, cause foam shrinkage making it necessary to carefully control the ratio of tin to silicone to obtain the desired open cell structure. This problem is referred to as "tin sensitivity".
In order to overcome the problem with the polysiloxane-polyoxyalkylene foam stabilizers, a mixture of an organosilicone oil, a hydrocarbon oil, and optionally a fatty acid ester is used (see U.S. Pat. No. 4,210,726). The hydrocarbon oil used in the mixture includes preferably alicyclic hydrocarbon oils and aromatic hydrocarbon oils and paraffin oils containing more than 20% by weight alicyclic hydrocarbon oil and/or aromatic hydrocarbon oil. The exemplified oils were cycloparaffinic (napthene) hydrocarbon oils. It is stated that other hydrocarbon oils do not exhibit good performance as foam stabilizers because of lack of compatibility with the foam composition. It is demonstrated that the combination of oils is important and that, without the cycloparaffinic hydrocarbon oil, the organsilicone oil separated from the polyol/water mixture.
While the use of this composition allowed the foam to be crushed, today only a small percentage of foam is crushed to open the cells. Rather the amount of tin catalyst to silicone surfactant used are carefully controlled, which can be limiting in terms of rise, gel, and cure times.
Accordingly, it would be economically desirable to provide a product which can be used as a partial or total replacement for the conventional surfactants used as foam stabilizers in both rigid and flexible foams. It would be particularly useful to replace all or part of the silicone surfactants used in flexible foams with a foam stabilizer which is not tin-sensitive.